Doctor blade assembly for dehydrating machine



March 22, 1960 s OVERTQN 2,929,155

DOCTOR BLADE ASSEMBLY FOR DEHYDRATING MACHINE 2 Sheets-Sheet 1 Filed Nov. 20, 1956 (we 6. az zera/v March 22, 1960 QVERTQN 2,929,155

DOCTOR BLADE ASSEMBLY FOR DEHYDRATING MACHINE Filed Nov. 20, 1956 2 Sheets-Sheet 2 Fig. 2

.Z .7775 27 far in: 6? Ovaerau United States Patent DOCTOR BLADE ASSEMBLY FOR DEHYDRATING MACHINE Lyle S. Overton, Dowagiac, Mich.

Application November 20, 1956, Serial No. 623,390 7 Claims. (Cl. 34-112) This invention relates generally to dehydrating machines and is directed more particularly to apparatus for dried material, such as sheets or films, from a heated rotating drum.

Specifically, the invention provides a doctor blade assembly including new and improved means for mounting a doctor or scraper blade in detachable relation upon a dehydrating machine so that the doctor blade may scrape different surface portions of a given quadrant of a dryer drum, and the doctor blade assembly may be reversed in an upside down "manner to scrape the surface of at least one other quadrant on the drum depending on where the material to be dried is applied to the drum.

Another aspect of this invention resides in the provision of a slidably mounted doctor blade assembly which is slidable with a slidably mounted dryer drum in a twin drum type dehydrating apparatus. The slidable drum dryer assembly including the doctor blade assembly has pressure responsive means which normally holds the slidable drum in a fixed spaced relationto the adjacent fixed drum but which will upon some hard substance coming between the drums permit spreading of the drums without damage to the apparatus.

Heretofore, the conventional manner of mounting the doctor blade assembly upon a dehydrating machine has been to aifix the assembly directly to the frame. The present type of construction has at least two distinct advantages'over the former manner of assembling the doctor blade assembly upon the machine. One advantage resides in that the doctor blade assembly may be reversible in an upside down manner to service at least two quadrants of a given drum depending on. where the material to be dried is appliedto thedrum. Also, the doctor blade may beadjusted to scrape the drum surface at difierent points about the drum periphery. These features are highly advantageous as the time interval for the drying of diiferent types of slurry fluids varies and the dried material must be removed at an opportune time or else the material is apt to become scorched. Still further, some dried materials have a tendency to roll 'up at the blades as they are scraped in one position, but will drop away from the drum by gravity when the blade contact is positioned at another position such as at the horizontal line through the center of the drum.

The second reason why the instant relationship between the drum dryer and the doctor blade assembly is believed to be highly advantageous is that the blade iii holder is at all times maintained completely in aligned relation with the associated drying drum. When a hard substance becomes lodged between the drums at the nip, the slidable drum and doctor blade assembly slides away from the fixed drum without the doctor blade being jammed against the sliding drum as was the case in former constructions when the doctor blade was permanently affixed to the frame and did not slide with the drum.

Accordingly, it is an object of this invention to ob- .viate the above set forth difliculties ar d provide a doctor ice blade assembly fordehydrating machines which may be easily and efficiently installed upona drum dryer, which may be elficiently operated to scrape .difierent types of dried material and which is simple and economical to manufacture.

Another object of this invention is to provide a doctor or scraper blade assemblies on dehydrating machines of the type having twin drying drums wherein one drum is slidable away from the other drum and with one doctor blade assembly being mounted in slidable relation on the slidable drum so that when the slidable drum is moved the doctor-blades will not be jammed into the surface of either of the drums. I

Another object of this invention is to provide a doctor blade assembly detachably mounted on a dehydrating machine along the'longitudinal axis of a dryer drum which assembly may be detached, turned upside down and remounted to scrape different quadrants of the drum depending on where the material to be dried is applied to the drum and with the doctor blade adjustable to scrape a given quadrant of the drum at different positions.

A further object of this invention is to provide a detachably mounted doctor blade assembly for scraping different quadrants of a drum depending on where the material to be dried is applied to the drum and which may be easily detached from the dehydrating machine and remounted.

Yet another object of this invention is to provide a drum drying machine of the type having closely spaced twin drums with an overhead darn, the drums each having a doctor assembly cooperable therewith, and wherein one drum and its associated doctor blade are slidable together away from the other drum without damage to the machine upon a hard substance becoming lodged in the nip spacing between the drums.

Other objects and features of this invention will more fully become apparent in view of the following detailed description taken in conjunction with the accompanying sheets of drawings illustrating several forms of my invention and in which:

Figure l is a fragmentary side elevation of my dehydrating machine;

Figure 2 is an end elevation showing in full and dotted lines my dehydrating machine; I

Figure 3 is an enlarged fragmentary detail view taken generally on the line IlI-III of Figure 1 looking in the direction indicated by the arrows; and

Figure 4 is a modified end elevation of a twin dryer drum type of dehydrating machine showing the reversible doctor blade of Figure 2 reversed and with a modified slurry reservoir construction.

As is shown in the drawings, the dehydrating apparatus includes a frame 10 having a pair of spaced supporting members 11 and 12 between which extend the various mechanisms for treating materials in a manner to be hereinafter described.

The drying mechanisms include closely spaced drying drums or cylinders 13 and 14. Drum 14 is mounted for rotation on shafts or co-axial extensions 15 and 16, these shafts having the ends thereof mounted for rotation in aligned bearings formed in slidable bearing blocks 17 and 18 (Fig. l). The bearing block 17 is shown in Figures 2 and 3 as having elongated relatively narrow slots 19 and 20 in feet 17a and 17b of the block 17. Bolts 21 and 22 are inserted through the slots 19 and 20 to slidably and adjustably clamp the blcck 17 to the frame 10. The block 18 is mounted upon the supporting member 12 in the same manner as the block 17.

Drum 13 is journalled and mounted upon the frame 10 in much the same manner as drum 14 only the slots are omitted in bearing blocks 23 and the blocks 23 are fixedly attached to the frame 10 by the bolts 21 and 22.

A conventional overhead 24 -is provided defining.

adjustment of the slidable blocks 17 and 18 on their respective bearings.

Any suitable drying medium such as hot air or steam may be passed intothe interior. of the drums in any suit- 7 able manner, and the' ma't erialto betreated may be suitably applied to the drum surfaces in any suitable manner. One form'of 'application'of material to the drum surfaces is shown in Figure 2 wherein the drum surfaces are rotated through the reservoir'of'fluid with the direction of rotation of the drums being indicated by the arrows in Figure 2. After the material is suitably spread on the drum surface, the material adheres to the drum surface as a thin filmor sheet in which condition it may be readily dried.

Doctor or scraper blade assemblies, generally designated by the numeral 35, coact with the drum surfaces on the ascending sides thereof to remove thethin film or sheet guide material from the drum surfaces. The scraper blade assembly may be of any suitable construction and the dried material removed from the drum surfaces by the blade assembly may be discharged and directed over the top edge of an apron into a conveyor trough disposed adjacent the drier drums. The drier drums 13 and 14 are rotated in an opposite direction relative to one another and may be driven in a conventional manner by means of a motor (not shown) connected to a suitable belt, chain, or gear driving arrangement.

The efliciency of the output of a dehydrating machine of the type herein disclosed depends to a great extent upon the efficiency of the removal of the treated or dried material from the drum. Therefore, it is important that substantially all of the dried material be removed from the drum surface as it passes the doctor blade assemblies 35, and it is important that the wear of'the blades in the drum surfaces is minimized.

The doctor or scraper blade assemblies each cornprise a doctor bar'36 disposed adjacent the'particular drier drum and parallel to the axis thereof. The ends of the doctor bar 36 are supported'by arms 371and.38. The arms 37 and 38 have spaced openings 39 and 40 through one of which is extended the end of'the doctor bar 36 and through the other of which is extended one of the shafts 15 or 16. The arms 37 and 38 are suitably fastened by screws 41-tothe outside faces of the blocks '17 and 18. If desired, the arms could be screwed to'the inside faces of the blocks 17 and18; The film of material on the drum surfaces is scraped off by the doctor or. scraper b'lade's" 42-held'by the doctor or holder bar 36. The primary pressure of the doctor blade 42 on the surfaces "of the drums may be altered by means of control wheels 43 having worms 43z'zwhich actuate worm wheels36atorockfthe doctor bar 36 on its pivotal mountings withrespect'to'thearms 37 and 38. It will be appreciatedthat thecontrolwheels are fixedly mounted on the'arrns37 and 38. and the doctor bar 36 is adapted to be rotated with respect to the arms 37 and 38 bymeans of turning the wheel thereby actuating the screw' linkage between the" arms and the doctor bar. 7

Variations of blade pressure along its length may be caused, for example, by uneven wear and variations permitted by manufacturingtolerances, and may be com: pensated for by means of an automa ic blade tension regulator} i i By. removing thecap screws 41 the arms 37 vand.,38

'may be rotated on the journal shafts so that the relative position of the doctor blade 42 may be varied with respect to the drum surface along the surface of a given quadrant of the drum. To service a different quadrant of the drum, where for example the method of applying the material to the drumis to be varied, the entire doctor blade assembly may be turned in an upside down manner, as is shown in Fig. 4, and refastened by means of the cap screws 41 to the bearing blocks. doctor blade '42 may also be brought about by altering its position with respect to the holder bar 36. This may be brought about by manipulating the screw which varies the tension between clampingvbar 36b and the holder bar 36. It will be appreciated in view of the foregoing that my doctor bladeconstruction is highly advantageous in view of the-large number of adjustments which may be made without interfering with the vacuum chamber; The above doctor blade assembly and drum relationship. is highly advantageous for drying various products. This is especially true since certain materials have different drying rates than other materials and must be removed at different times fromthe drum toprevent scorching. Also, some materials have a tendency to roll up at the blades when they are in one position. but will drop away from the drum by gravity when the blade contact is in a different position, for example, when the blade contact is on a horizontal line through the center of the drum.

As is best seen in Figure 1, a block 42a is fixedly fastened to the supporting blocks 11 and 12 of the frame 10. Since the relationship of the blocks 42a with respect to the bearing blocks 17 and 18 is the same in each case, a description of one is believed'to sufilce for both. Connected to the block 42a is a second block or collar 44 having a central opening 44a extending vertically therethrough. An opening 45 extends horizontally through both of the blocks 42a and 44 with the opening 45 intersectingthe collar opening 44a. Extending through the blocks 42a and 44 and threaded into the foot 17b of the bearing'block 17 is a bolt 46. .The bolt 46 has an intermediate vertical opening 47 which when the bolt is in assembly upon the machine, is in alignment with the vertical opening 44:: in a collar 44. Extending through the openings 44a and 47 is a shear pin 48.

Inview of the foregoing, it will now be appreciated that the slotted bearings 19 and 20 allow the entire drum assembly 14 includingthe bearing, blocks 17 and 18 and. the doctor bar. assembly 35 to move about three quarters of an inch,.b0th for adjustmentof the nip spacingv and to permit spreading of the drums should some hardsubstance come between the drums. The shear pins 48 normally maintain the bearing blocks 17 and 18 in predetermined relation to the supporting members 11.and.12.to regulate the nip spacing. If some hard substance becomes lodged in the nip 31 the drum 14 is caused to moveaway from the drum 13 with the bolt 46 breaking the shearppin 48 thereby eliminating the possibility of damage :to the. drum surfaces by extra blade pressure when the drum spacing is increased to the doctor blade assembly 35. This is contrasted with former constructions where the doctor blade assembly is not permitted to. slide with thebearing blocks 17 and .18.

Gther means maybe used for controlling the spacing betweenthe drumssuch as tension springs wherein the springs would. have enough strength to hold the drum in position during normal operation, but would collapse when the pressure was in excess'of a predetermined amount. Still another means would be through the use of a'hydraulic jack which releases the pressure at a predetermined point.

Shown in Figure 4 is a modified twin drum drying machine 50 of thetype having a splash or dip feeding arrangementwhere the drums (only one being shown) are rotated in the opposite direction indicated by'the' ar- Adjustment of the row as compared to the direction or rotation ofthe drums of the other machine shown in Figure 2.

Identical elements have again been identified by the same numerals as in the machine shown in Figures l-3.

The same doctor blade assembly 35 has been again used only the assembly has been reversed and installed upside down as compared with manner of installation shown in Figure 2 with the frame being notched at 51 to permit the assembly to scrape the lower quadrant of the drum 13. In this instance, an under feeding device or pan 52 is supported by the frame 10 and the drums may either be dipped into the pan or a splasher device may splash and coat the surface of the drum.

It will be understood that modifications and variations may be eifected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. In a drum drying machine, a frame, a heated drum rotatably mounted along its longitudinal axis on said frame, said machine having a slurry reservoir with the surface of said drum being at intervals coated as it comes into contact with the slurry in the reservoir, an upside down reversible doctor blade assembly scraping predetermined different quadrants of said drum, said assembly. having a pair of arms for supporting a doctor blade on said machine with one arm on each side of said drum, and fasteners connecting said arms to said machine with said arms extending radially from the longitudinal axis of said drum, said fasteners being adjustable with the doctor blade assembly being circumferentially swingable to varying predetermined scraping positions on one quadrant of the drum and to varying predetermined scraping positions on at least one other quadrant of said drum.

2. In a drum drying machine including a frame, sets of bearing blocks on said frame, a twin pair of heated drums each rotatably mounted along its longitudinal axis on one of said sets of bearing blocks, said machine having a slurry reservoir with the surfaces of said drums being coated as they come into contact with the slurry in the reservoir, two doctor blade assemblies on said machine with one assembly cooperable with each of said drums, each assembly having a pair of supporting arms with one arm on each side of said drum, and detachable fasteners connecting said arms to said machine with said arms extending radially from the longitudinal axis of the associated drum, said assemblies upon detachment of said fasteners being circumferentially movable to difierent positions about said drums to facilitate drying and unloading difierent type slurry fiuids.

3. In a drum drying machine including a frame, sets of bearing blocks on said frame, a twin pair of heated drums each rotatably mounted along its longitudinal axis on one of said sets of bearing blocks, said machine having a slurry reservoir with the surfaces of said drums being coated as they come into contact with the slurry in the reservoir, and two doctor blade assemblies on said machine each having a pair of radially extending supporting arms with one arm on each side of said drum and detachably fastened to said machine along the longitudinal axis of the associated drum and with the axis of said drum in parallelism with the axis of the other of said drums, said doctor blades being circumferentially swingable about the axes of the drums for scraping different quandrants of the drums.

4. in a drum drying machine including a frame, bearing blocks on said frame, at least one heated drum rotatably mounted along its longitudinal axis on said blocks, said machine having a slurry reservoir with the surface of said drum being at intervals coated as it comes into contact with the slurry in the reservoir, a doctor blade assembly on said machine having a pair of arms for supporting a doctor blade with one arm on each side of said drum, and fasteners connecting said arms to said machine with said arms extending radially from the longitudinal axis of said drum, said fasteners beingadjustable with the doctor blade assembly being circumferentially swingable to different scraping positions about the perimeter of said drum.

5. In a drum drying machine, a frame, a pair of close ly spaced heated drums having a nip space therebetween and each rotatably mounted along its longitudinal axis, supporting block structure carrying one of said drums with said supporting block structure and the drum it carries being slidably mounted on said frame, an overhead dam on said frame including darn portions cooperable with said drums to provide a slurry reservoir with the surfaces of said drums being coated as they come in contact with the slurry, a doctor blade assembly cooperable with each of said drums with each assembly having longitudinally spaced supporting arms for carrying the assembly upon the machine, said doctor blade assembly cooperable with said slidable drum being connected to said supporting block structure and slidable therewith, and pressure responsive means between said slidable drum and said frame normally holding said slidable drum in a predetermined spaced position relative to the other of said drums and responsive upon the development of pressure in excess of a predetermined amount to permit movement of the slidable drum away from the other drum without damaging the drum surfaces or the doctor blade assemblies, said means including an extension slidable with said slidable drum and a shear pin normally barring movement of said extension and said slidable drum but upon shearing of said pin permitting said slidable drum to move away from the other drum.

6. In a drum drying machine, a frame, a pair of closely spaced heated drums having a nip space therebetween and each rotatably mounted along its longitudinal axis, supporting block structure carrying one of said drums with said supporting block structure and the drum it carries being siidably mounted on said frame, an overhead dam on said frame including dam portions cooperable with said drums to provide a slurry reservoir with the surfaces of said drums being coated as they come in contact with the slurry, a doctor blade assembly cooperable with each of said drums with each assembly having longitudinally spaced supporting arms for carrying the assembly upon the machine, said doctor blade assembly cooperable with said slidably drum being connected to said supporting block structure and slidable therewith, pressure responsive means between said slidable drum and said frame normally holding said slidable drum in a predetermined spaced position relative to the other of said drums and responsive upon the development of pressure in excess of a predetermined amount to permit movement of the slidable drum away from the other drum without damaging the drum surfaces or the doctor blade assemblies, and fastening means fastening said arms to said machine with said arms being slidable with said drum, said fasteners being adjustable with the doctor blade assembly being swingable to varying predetermined scraping positions on one quadrant of the drum and to varying predetermined scraping positions on at least one other quadrant of said drum.

7. in a twin drum type dehydrating machine including a. frame, a first drum rotatably mounted on said frame, bearing block structure slidably mounted on said frame, a second drum spaced from said first drum rotatably mounted on said block structure and slidable therewith, said machine having a slurry reservoir with the surfaces of said drums being coated as they come into contact with the slurry in the reservoir, said slidable block structure and said slidable drum comprising a slidable drum as sembly, a doctor blade assembly on said machine having a pair of radially extending arms for supporting a doctor blade with one arm on each side of said second drum, fasteners connecting said arms to said slidabledrum as sembly, said fasteners being adjustable with the doctor blade as sembly being swingableltoavaryig g, predetermined p'dsitioriswith respect to saidxsecond drum; and 'pte'a'sure responsive means between said slidabledrum assembly. and said frame normally holding said second drum: in a predetermined spaced position relative to the. first drum and responsive upon. the development of pressure. in ex.- cess of a predetermined amount permitting: movement of the slidable drum assembly away from the first drum without damaging the drum surfaces. I

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